Electrode catheters have been in common use in medical practice for many years. They are used to stimulate and map electrical activity in the heart and to ablate sites of aberrant electrical activity.
In use, the electrode catheter is inserted into a major vein or artery, e.g., the femoral artery, and then guided into the chamber of the heart which is of concern. Within the heart, the ability to control the exact position and orientation of the catheter tip is critical and largely determines how useful the catheter is.
Steerable catheters are generally well-known. For example, U.S. Pat. No. RE 34,502 describes a catheter having a control handle comprising a housing having a piston chamber at its distal end. A piston is mounted in the piston chamber and is afforded lengthwise movement. The proximal end of the catheter body is attached to the piston. A puller wire is attached to the housing and extends through the piston and through the catheter body. The distal end of the puller wire is anchored in the tip section of the catheter to the side wall of the catheter shaft. In this arrangement, lengthwise movement of the piston relative to the housing results in deflection of the catheter tip section. The design described in U.S. Pat. No. RE 34,502 is generally limited to a catheter having a single puller wire.
Bidirectional steerable catheters are also generally well-known, as a variety of designs have been proposed. In many such designs, e.g., as described in U.S. Pat. Nos. 6,066,125, 6,123,699, 6,171,277, 6,183,463 and 6,198,974, all of which are incorporated herein by reference, a pair of puller wires extend through a lumen in the main portion of the catheter shaft and then into opposing off axis lumens in a deflectable tip section where the distal end of each puller wire is attached to the outer wall of the deflectable tip. Pulling one wire in a proximal direction causes the tip to deflect in the direction of the off axis lumen in which that wire is disposed.
In other designs, e.g., as described in U.S. Pat. No. 5,531,686, the puller wires are attached to opposite sides of a rectangular plate that is fixedly mounted at its proximal end and extends distally within a lumen in the tip section. In this arrangement, pulling one of the wires proximally causes the rectangular plate to bend in the direction of the side to which the pulled puller wire is attached, thereby causing the entire tip section to deflect.
In all of the designs for a steerable catheter, the puller wire or wires are attached at their distal ends to some structure in the tip section of the catheter. Such designs require time, effort and expense to make such attachments. It would be useful to provide a steerable tip catheter that does not require that the puller wires be fixedly attached to the catheter tip section.